Treatment of polyphenyl thioethers with alkali metals and oxygen gas



United States Patent 3,532,758 TREATMENT OF POLYPHENYL THIOETHERS WITH ALKALI METALS AND OXYGEN GAS Carl W. Gieseking, St. Louis, Mo., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Jan. 26, 1968, Ser. No. 700,728 Int. Cl. C07c 149/02 U.S. Cl. 260-609 11 Claims ABSTRACT OF THE DISCLOSURE A process for the treatment of polyphenyl thioethers to improve their color, odor and oxidative stability and to decrease their corrosiveness to metals wherein the thioether is contacted with a contacting agent selected from the group consisting of alkali metals and an oxygen containing gas.

This invention relates to the treatment of certain polyphenyl thioethers which can also be classed as polyphenyl sulfides, which term is meant to include polyphenyl sulfides in which one or more, but not all, of the sulfur atoms have been replaced with oxygen atoms, to improve their color, odor and oxidative stability and to decrease their corrosiveness to metals.

Because of the wide variety of applications under which functional fluids are utilized, a concurrence of many properties, both physical and chemical, are needed in a particular fluid to provide the service demanded. One of the most rigorous demands on fluids is made by gas turbine aircraft hydraulic systems and gas turbine engine lubrication systems. As the speed and altitude of operation of jet powered aircraft increases, lubrication problems also increase because of higher operating temperatures and higher bearing pressures resulting from the increased thrust needed to obtain higher speeds and altitudes. As the service conditions encountered become increasingly severe, the useful life of the functional fluid is, of course, shortened.

The useful life of any lubricant or hydraulic fluid can be adjudged on the basis of many criteria such as the extent of viscosity increase, the extent of corrosion to metal surfaces in contact with the lubricant and the extent of engine deposits. Those skilled in the art have found various ways to improve lubricants and to thus retard or prevent the effects which shorten the useful life of a lubricant. Thus, for example, small amounts of other materials, or additives, can be added to lubricants in order to effect one or more of the properties of the base lubricant. Oftentimes, however, it is diflicult, especially as operating temperatures are increased, to find additives which will still perform the function for which they are added and yet not inject other problems.

Polyphenyl thioethers have been proposed as compounds which can be employed as functional fluids in many different types of application, such as hydraulic fluids, damping fluids, synthetic lubricants and atomic reactor coolants.

It has now been found that the oxidative stability and thus the useful life of polyphenyl thioethers can be greatly extended, even under the severe conditions encountered in jet engines and other devices operating at temperatures of the order of 500 F. and higher, by contacting such thioethers in the liquid phase with a contacting agent selected from the group consisting of alkali metals and an oxygen containing gas, that is, metals of Group Ia of the Periodic Table of Elements as shown in Handbook of Chemistry and Physics, published by the Chemical Rubber Publishing Company, 42nd edition, pp. 448 and 449 and gases such as air or oxygen enriched air are use- 3,532,758 Patented Oct. 6, 1970 ful in the process of this invention. Also, by the process of this invention, significant improvements in the color and odor of such thioethers are realized and their corrosiveness toward certain metals is significantly reduced.

It is, therefore, an object of this invention to provide a method for increasing the oxidation resistance of polyphenyl thioethers and compositions thereof. Another object is to provide polyphenyl thioethers and compositions thereof which have decreased metal attack and give decreased formation of engine deposits. Still another ob ject of this invention is to provide a process to improve the color and odor of polyphenyl thioethers.

As used herein the term polyphenyl thioether includes a compound or physical mixture of compounds represented by the formula Aam wherein .A, A A and A are each a chalkogen having an atomic number of 8 to 16, provided at least one of A, A A and A has an atomic number of 16, X, X X X and X each are selected from the group consisting of hydrogen, alkyl, haloalkyl, halogen, arylalkyl and substituted arylalkyl, L, m and n are whole numbers each having a value of from O to 8 and a is a Whole number having a value of from 0 to 1 provided that when a is 0, m is a whole number having a value of from 1 to 2. Typical examples of alkyl and substituted alkyl radicals are given below. Examples of such polyphenyl thioethers are:

TV I

where m is a whole number from 0 to 6,

III

Where A and A are each selected from oxygen and sulfur W er -mi s.

where x and y are whole numbers from 0 to 3 and the sum of x+y is from 1 to 6 and A and A are each selected from oxygen and sulfur but at least one of A and A is sulfur. Specific examples of polyphenyl thioethers are:

2-phenylmercapto-4-phenoxydiphenyl sulfide 2-phenylmercapto-3-phenoxydiphenyl sulfide 2-phenoxy-3'-phenylmercapt0diphenyl sulfide 3-phenoxy-4'-phenylmercaptodiphenyl sulfide 2-phenoxy-4'-phenylmercaptodiphenyl sulfide 2-phenoXy-2-phenylmercaptodiphenyl sulfide 3 o-Bis (phenylmercapto benzene p-Bis (phenylmercapto benzene Phenylmercapto(phenoxy) biphenyl Bis(o-phenylmercaptophenyl) sulfide Bis (p-phenylmercaptophenyl) sulfide Bis(m-phenylmercaptophenyl) sulfide 1,2,3-tris (phenylmercapto) benzene 1-phenylmercapto-2,3-bis (phenoxy benzene 1,2,4-tris (phenylmercapto benzene 1, 3,5 -tris phenylmercapto benzene o-Bis (o-phenylmercaptophenylmercapto benzene p-Bis (p-phenylmercaptophenylmercapto benzene p-Bis (o-phenylmercaptophenylmercapto benzene p-Bis (m-phenylmercaptophenylmercapto benzene m-Bis (p-phenylmercaptophenylmercapto benzene o-Bis (p-phenylmerc aptophenylmercapto benzene ar-Bis (phenylmercapto -ar- (phenylmercapto benzene 2,2'-bis (phenylrnercapto diphenyl ether 2 3 '-bis (phenylmercapto diphenyl ether 2,4'-bis (phenylmercapto diphenyl ether 4,4-bis (m-tolylmercapto diphenyl ether 3,3 -bis m-tolylmercapto) diphenyl ether 2,4'-bis (m-tolylmercapto diphenyl ether 3,4-bis (m-tolylmercapto diphenyl ether 3,3 -bis (p-tolylmercapto diphenyl ether 3,3'-bis (xylylmercapto) diphenyl ether 4,4'-bis (xylylmercapto diphenyl ether 3,4'-bis (xylylmercapto) diphenyl ether 3,4'-bis (m-isopropylphenylmercapto diphenyl ether 3,3'-bis (m-isopropylphenylmercapto) diphenyl ether 2,4'-bis (m-isopropylphenylmercapto) diphenyl ether 3 ,4'-bis (p-tert.-butylphenylmercapto diphenyl ether 4,4'-bis (p-tert.-butylphenylmercapto) diphenyl ether 3 ,3 '-bis (p-tert.-butylphenylmercapto diphenyl ether 3,3'-bis (m-di-tert.-butylphenylmercapto) diphenyl ether 3,3 '-bis m-chlorophenylmercapto diphenyl ether 4,4-bis (m-chlorophenylmercapto) diphenyl ether 3 ,3-bis (m-trifiuoromethylphenylmercapto) diphenyl ether 4,4'-bis (m-trifiuoromethylphenylmercapto diphenyl ether 3,4-bis (m-trifluoromethylphenylmercapto diphenyl ether 2,3'-bis (m-trifluoromethylphenylrnercapto diphenyl ether 3,3 '-bis (p-trifiuoromethylphenylmercapto) diphenyl ether 3 ,3-bis o-trifiuoromethylphenylmercapto) diphenyl ether 3,3 -bis (m-methoxyphenylmercapto diphenyl ether 3,4'-bis (m-isoproproxyphenylmercapto diphenyl ether 3,4-bis(m-perfluorobutylphenylmercapto) diphenyl ether 2-m-tolyloxy-2-phenylmercaptodiphenyl sulfide 2-p-tolyloxy-3-phenylmercaptodiphenyl sulfide 2-o-tolyloxy-4-phenylmercaptodiphenyl sulfide 3-m-tolyloxy-3-phenylrnercaptodiphenyl sulfide 3-m-tolyloxy-4'-phenylmercaptodiphenyl sulfide 4-m-tolyloxy-4-phenylmercaptodiphenyl sulfide 3-xylyloxy-4-phenylmercaptodiphenyl sulfide 3-xylyloxy-3'-phenylmercaptodiphenyl sulfide 3-phenoxy- -m-tolylmercaptodiphenyl sulfide 3-phenoxy-4-m-tolylmercaptodiphenyl sulfide 2-phenoxy-3-p-tolylmercaptodiphenyl sulfide 3-phenoxy-4'm-isopropylphenylmercaptodiphenyl sulfide 3-phenoxy-3'-m-isopropylphenylmercaptodiphenyl sulfide 3-m-toloxy-3'-m-isopropylphenylmercaptodiphenyl sulfide 4-m-trifluoromethylphenoxy-4'-phenylmercaptodiphenyl sulfide 3-m-trifluoromethylphenoxy-4'-phenylmercaptodiphenyl sulfide 2m-trifluoromethylphenoxy-4-phenylmercaptodiphenyl sulfide 3-m-trifluoromethylphenoxy-3 '-phenylmercaptodiphenyl sulfide 3-p-chl0rophenoXy-3'-phenylmercaptodiphenyl sulfide and 3-m-bromophenoxy-4-phenylmercaptodiphenyl sulfide Mixtures of polyphenyl thioethers can also be treated according to the method of this invention. A typical ex ample of a mixture of polyphenyl thioethers is one which contains by weight from about 45% to about 55% 4 m-phenoxyphenyl m-phenylmercaptophenyl sulfide, from about 25% to about 35% bis(m-phenylmercaptophenyl) sulfide and from about 18% to about 25% bis(m-phen oxyphenyl) sulfide.

Preferred polyphenyl thioethers of this invention are mixtures of m-bis(phenylmercapto)benzene and certain other materials which have properties that make them well suited for the uses disclosed above and particularly those applications, such as jet engine lubricants, requiring high temperatures, thermal and oxidative stability and wide liquid range.

Such other materials can advantageously be employed in amounts of from about 20 to about 200 parts by weight per parts of m-bis(phenylmercapto)benzene. The other materials contemplated to be used with m-bis (phenylmercapto)benzene to provide such mixtures are as follows:

(a) The three-, four-, fiveand six-ring polyphenyl thioethers, for example o-bis(phenylmercapto)benzene bis(m-phenylmercaptophenyl) sulfide W O U O O m-phenylmercaptophenyl-p-phenylmercaptophenyl sulfide,

the trisphenylmercaptobenzenes,

such as 1,2,4-triphenylmercaptobenzene. 3,3-bis (phenylmercapto)biphenyl IX W 57 m-bis (p-phenylrnercapt0phenylmercapto benzene,

m-bis (m-phenylmercaptophenylmercapto benzene (b) The mixed polyphenyl oxy-thioethers having the wherein R is a phenyl group, R is a phenylene group and Y and Y are each selected from the group consisting of oxygen and sulfur, providing at least one of Y and Y is sulfur and c is a whole number from 1 to 5. Examples of such mixed polyphenyl oxythioethers are m-phenylmercaptodiphenyl ether 3,3-bis (phenylmercapto diphenyl ether,

il ilflfl 3,3 '-bis (phenoxy) diphenyl sulfide,

XV ETUTW 3-phenoxy-3-phenylmercaptodiphenyl sulfide,

@Tlilfl 3-phenylmercapto-3-pl1enoxydiphenyl ether,

(lflflil 3,4'-bis (phenylmercapto) diphenyl ether,

@ flil il m-bis (m-phenylrnercap tophenoxy) benzene,

XIX

E ]s@o J-s E Ts and 3 phenylmercapto 3' (m phenylmercaptophenylmercapto)dipheny1 ether,

XX Kl Q Kl O- O (c) The four-, fiveand six-ring polyphenyl ethers which can be represented by the structure was XXI

Of the various possible mixtures described above, cer tain more limited compositions are preferred because of wider liquid range and in many cases unexpectedly low evaporation losses as well as other properties which make such compositions well suited for lubricants for jet engines. The more limited, preferred compositions referred to are listed in Table I below.

TABLE I Percent by weight No. Components range 1 m-Bis (pheuylmercapto)benz ene 80-70 A mixture of ab out- 65% m-bis (m-phenoxyphenoxy)benz ene m-[ (m-phenoxyphenoxy) (p-phenoxy- 20 30 phenoxyflbeuzene 5% m-b1s (p-phenoxyph enoxy)benz eue 2 .m-Bis (phenyhnercapto)benz one 5545 IH-BlS (phenoxy) diphenyl sulfide 45-55 3. m-B is (phenylmereapto)benzene 65-35 3-phenoxy-3-phenylmercaptodiphenyl sulfide- -65 4. m-Bis (phenylmereapt 0)benzene 66-45 m-B is (phenylmercaptophenyl) sulfide.-. 18- 6 m-Bis(phenoxy)diphenyl sulfide -27 5 m-Bis(pheuylmereapto)benzene -45 m-Bis (phenylmerca tophenyl) sulfide 20 6 8phenoxy-3-pheny mercaptodiphenyl sulfide. 43-23 6 m-Bis(phenylmercapto)benzene -42 Iu-Bis (phenylmercaptophenyl) sulfide 25- 5 m-B is (phenyhnercaptophenyl) ether 43-15 7. m-Bis (phenylmercapto)benzene 57-43 m-Bis(phenylmeroaptophenyl) sulfide 23- 5 m-Phenylmereaptophenyl-p-phenylmercapto- 48-25 phenyl sulfide.

8- m-Bis (phenylmercapto)benz ene 54-43 m-Phenylmercaptodiphenyl ether- 32-19 o-Bis (phenylmercapto)benzene. 31-22 9. m-Bis(phenylmercapto)benzene 55-45 Ill-Bis (phenylmercaptoph enyl) sulfide 20-10 3-phenoxy-3-phenylmercaptodipheuyl sulfide- 30-10 m-Bis (phenoxy) diphenyl sulfide 30-10 The term metal as used herein is intended to include the elemental form thereof. Most metals of Groups Ia are commercially available in many forms such as flake, chip, crystal, sheet and granules, any of which can be used in the process of this invention. The preferred metals are sodium and potassium.

In carrying out the process of this invention to prepare improved polyphenyl thioethers, the contacting of the fluid can be effected by means known to the art for contacting liquids with solids or gases, e.g., by agitating a mixture of the fluid and the metal or gas; by passing the fluid through a packed column of the metal or by sparging the oxygen containing gas through the fluid. Thus, as used in the specification and claims, contact is intended to mean the use of force which acts upon either the liquid, metal or oxygen containing gas. Examples of such force are agitation'of the fluid and the sparging of the oxygen containing gas through the fluids. The fluid can be recovered after treatment by means known to the art for separating liquids from solids as by filtration or by distilling the liquid from the treatment vessel under reduced pressure.

Generally the improvements in the fluid properties obtained by the process of this invention are unaifected by the concentration of the metal, the time of contact or the temperature; however, it should be realized that there are minimum values of concentration, time and temperature below which the process of this invention becomes impractical. A minimum concentration of metal of about 0.01% by weight of polyphenyl thioether to be treated should be used. On the other hand, the benefits obtained are effected, by particle size. The extent of the benefit obtained appears to increase as the particle size of the metal decreases. The length of time of contact will vary depending upon variances in the particle size but a minimum time of about one hour at about 25 C. should be used. In general, times in the order of 1 to 48 hours are suflicient for most conditions.

The temperature at which the process of this invention is carried out can vary from about 25 C. to 350 C. or higher. The choice of a particular temperature will be dictated, for example, by time available, by the facili ties available, particle size and amount of the metal and the characteristics of the fluid being treated. For example, when using the metal in amounts of from 0.5 to 1% by weight of the fluid a contact period of from about 1 to 5 hours at temperatures in the range of about 100 C. to about 300 C. provide the optimum efficiency of equipment and benefit to the fluid.

The mechanism through which the improvements in the properties of the ethers treated according to the method of this invention occurs is not completely understood at this time. However, such improvements are wholly unexpected in view of the lack of purifying capability known or attributed to such metals and gases such as an adsorption mechanism. Particularly unexpected are the improvements in the color and odor of the abovedescribed fluids brought about by the process of this invention.

Of the metals in Groups In of the Periodic Table of Elements, potassium is most preferred in the process of this invention because of its low cost and general availability in many forms. More particularly potassium powder has been found to be best suited for the process of this invention although if the process is operated at temperatures above the melting point of the metal the initial form is inconsequential.

The following non-limiting examples illustrate the process of this invention.

EXAMPLE 1 Into a suitable boiling flask equipped with temperature sensing means, a distillation column and means for agitating the contents there were charged 150.0 grams of m-bis(phenylmercapto)benzene and 0.15 gram of potassium metal. The mixtures was heated under nitrogen to about 200 C. and held at about that temperature for two hours during which time the mixture was agitated. The metal was separated from the fluid by filtration through a course glass filter. The thus treated fluid had very little odor as compared to the untreated fluid and had a comparatively lighter color.

EXAMPLE 2 In a suitable boiling flask equipped as described in Example 1, 150 grams of 3,3'-bis(phenylmercapto) diphenyl ether is contacted with potassium metal in the manner of Example 1, except the temperature is 25 C. and the contact time is 24 hours. A fluid having improved odor, color and oxidative stability is obtained.

Separate samples of m-bis-(phenylmercapto) benzene, hereinafter designated as fluid A, were treated by contacting them with other metals of this invention in the manner of Example 1. Also, in similar manner, a fluid hereinafter designated fluid B, consisting by weight of about 50% m-bis(phenylmercapt0)benzene, 11% m-bis (phenoxy)diphenyl sulfide, 15% m-bis(phenylmercaptophenyl) sulfide and 24% 3-phenoxyphenyl 3'-phenylmercaptodiphenyl sulfide was treated by contacting separate samples with potassium. The results of the treatments are reported below in Table II. In each case results similar to that stated in Example 1 were obtained with regard to odor.

The data reported in Table II was obtained employing one of the major bench scale methods used for evaluating the oxidative stability of a lubricant. The procedure is described in Federal Test Specification 791, Method 5308, excepting that the fluid to be tested is heated to a temperature of 50% F. for a period of 48 hours instead of 250 F. for 168 hours in the presence of certain metals and oxygen. The viscosity increase of the lubricant is determined. Additionally, information as to the corrosiveness of a lubricant to metals can also be obtained. In order to demonstrate the effectiveness of the process of this invention in improving the oxidative stability and reduced corrosiveness of the fluids, samples of the fluid treated as in the above example and untreated samples of the same fluids were tested. The metal specimens used were steel, copper, silver, titanium, magnesium alloy and aluminum alloy. However, only the results upon copper and silver are reported since the untreated compositions tested had essentially no effect on steel, magnesium alloy, titanium and aluminum alloy. Viscosity measurements were made according to ASTM Method D-445-S3T using a Cannon-Fenske modified Ostwald viscosimeter. The percent viscosity increase was determined by measuring the viscosity of the samples before and after the test, dividing the difference by the original viscosity and multiplying the quotient by 100. The corrosiveness to metals was determined by weighing metal specimens of known size before and after the test.

1 Percent by weight of fluid.

According to the data in Table II above the reduction in viscosity increase indicates the increased oxidative stability of polyphenyl thioethers brought about by contacting such thioethers with alkali metals. In addition the corrosiveness to copper and silver were greatly reduced.

EXAMPLE 10 Into a suitable flask equipped with temperature sensing means, a distillation column, heating means and means for introducing gas there was placed 1000 grams of mbis(phenylmercapto)benzene which was then heated to a temperature of about 200 C. A small amount of low boiling material was removed at about 185 C. Air was sparged into the fluid through a tube extending to the bottom of the flask for a period of 16 hours at a rate of 175 ft. /hrs. while the temperature was maintained at about 200 C. The fluid was then distilled from the flask at a temperature range of 187 C. to 193 C. and the oxidative stability of the fluid was determined according to the above described procedure. Accordingly, the fluid was found to have a viscosity increase at C. of 3.6% whereas another sample of the test fluid, treated as above except for air sparging was found to have a viscosity increase at 100 C. of 8.5%.

Similar results can be obtained by employing the procedure of Example 8 but at temperatures of from 25 C. to 300 C. or above. Contact time of from 1 to 24 hours can be employed and gas flow rate regulated to suit the equipment used and desired contact time. Thus, gas flow rate can range from 50 to 500 ft. /hrs. but usually range from 200 ft. /hrs. over a period of from 2 to 8 hours at a temperature of from about 150 C. to 250 C.

Contact time can be reduced by employing oxygen enriched air. In addition, any inert carrier gas can be employed in admixture with oxygen. Thus, gases such as carbon dioxide, nitrogen or helium containing oxygen in the range of from 5% to 50%, by volume can be employed.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited to such examples and embodiments and that it can be variously practiced Within the scope of the following claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for improving the oxidative stability and color of polyphenyl thioethers which comprises contacting a polyphenyl thioether in the liquid phase at a temperature of at least 25 C. with a contacting agent selected from the group consisting of alkali metals wherein the alkali metal is present in an amount of at least 0.01% by weight of said polyphenyl thioether and an oxygen containing gas wherein oxygen is present in amounts of from about 5% to about 50% by volume and is bubbled through said polyphenyl thioether.

2. The process of claim 1 wherein the contacting agent is an alkali metal.

3. The process of claim 1 wherein the contacting agent is an oxygen containing gas.

4. The process of claim 1 wherein the contacting is performed at a temperature in the range of from about 100 C. to about 350 C.

5. The process of claim 2 wherein the contacting is performed at a temperature of from about 100 C. to about 350 C.

6. The process of claim 1 wherein the polyphenyl thioether is represented by the formula:

| X I i X2 I wherein A, A A and A are each a chalkogen having an atomic number of 8 to 16, provided at least one of A, A A and A has an aromatic number of 16, X, X X X and X each are selected from the group con sisting of hydrogen, alkyl, haloalkyl, halogen, arylalkyl and substituted arylalkyl, L, m and n are whole numbers each having a value of from 0 to 8 and a is a while number having a value of from 0 to 1 provided that when a is 0, m is a whole number having a value of from 1 to 2.

7. The process of claim 4 wherein the polyphenyl thioether is represented by the formula:

nL/Ll LV in where m is a whole number from 0 to 6, A and A are each independently selected from the group consisting of oxygen and sulfur provided at least one of A and A is sulfur.

8. The process of claim 4 wherein the polyphenyl thioether is represented by the formula:

wherein R is a phenyl group, R is a phenylene group and Y and Y are each selected from the group consisting of oxygen and sulfur provided at least one of Y and Y is sulfur and c is a whole number from 1 to 5 and (2) mixtures of (1).

11. The process of claim 5 wherein the oxygen containing gas is air.

References Cited UNITED STATES PATENTS 5/1967 Campbell et al. 260609 XR 2/ 1969 Campbell 260609 CHARLES B. PARKER, Primary Examiner D. R. PHILLIPS, Assistant Examiner US. Cl. X.R. 260611 

